/*===========================================================================*
 *                                                                           *
 *  sflmath.c -                                                              *
 *                                                                           *
 *  Copyright (c) 1991-2003 iMatix Corporation                               *
 *                                                                           *
 *  ------------------ GPL Licensed Source Code ------------------           *
 *  iMatix makes this software available under the GNU General               *
 *  Public License (GPL) license for open source projects.  For              *
 *  details of the GPL license please see www.gnu.org or read the            *
 *  file license.gpl provided in this package.                               *
 *                                                                           *
 *  This program is free software; you can redistribute it and/or            *
 *  modify it under the terms of the GNU General Public License as           *
 *  published by the Free Software Foundation; either version 2 of           *
 *  the License, or (at your option) any later version.                      *
 *                                                                           *
 *  This program is distributed in the hope that it will be useful,          *
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of           *
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            *
 *  GNU General Public License for more details.                             *
 *                                                                           *
 *  You should have received a copy of the GNU General Public                *
 *  License along with this program in the file 'license.gpl'; if            *
 *  not, write to the Free Software Foundation, Inc., 59 Temple              *
 *  Place - Suite 330, Boston, MA 02111-1307, USA.                           *
 *                                                                           *
 *  You can also license this software under iMatix's General Terms          *
 *  of Business (GTB) for commercial projects.  If you have not              *
 *  explicitly licensed this software under the iMatix GTB you may           *
 *  only use it under the terms of the GNU General Public License.           *
 *                                                                           *
 *  For more information, send an email to info@imatix.com.                  *
 *  --------------------------------------------------------------           *
 *===========================================================================*/

#include "prelude.h"                    /*  Universal header file            */
#include "sflmath.h"                    /*  Function prototypes              */


/*  ---------------------------------------------------------------------[<]-
    Function: point_in_rect

    Synopsis: Checks if the requested FPOINT is within the specified
              rectangle.  Returns TRUE or FALSE appropriately.
    ---------------------------------------------------------------------[>]-*/

int
point_in_rect (const FPOINT *point, const FPOINT *coords)
{
    return ((point-> x >= coords [0].x && point-> x <= coords [1].x)
         && (point-> y >= coords [0].y && point-> y <= coords [1].y));
}


/*  ---------------------------------------------------------------------[<]-
    Function: point_in_circle

    Synopsis: Checks if the requested FPOINT is within the specified
              circle.  Returns TRUE or FALSE appropriately.
    ---------------------------------------------------------------------[>]-*/

int
point_in_circle (const FPOINT *point, const FPOINT *coords)
{
    double
        circle_radius,
        distance_from_centre;

    circle_radius        = ((coords [0].y - coords [1].y) *
                            (coords [0].y - coords [1].y)) +
                           ((coords [0].x - coords [1].x)  *
                            (coords [0].x - coords [1].x));

    distance_from_centre = ((coords [0].y - point-> y) *
                            (coords [0].y - point-> y)) +
                           ((coords [0].x - point-> x) *
                            (coords [0].x - point-> x));
    return (distance_from_centre <= circle_radius);
}


/*  ---------------------------------------------------------------------[<]-
    Function: point_in_poly

    Synopsis: Checks if the requested FPOINT is within the specified
              polygon.  Returns TRUE or FALSE.
    ---------------------------------------------------------------------[>]-*/

int
point_in_poly (const FPOINT *point, const FPOINT *pgon, int nbpoints)
{
    int
        inside_flag,
        xflag0,
        crossings;
    const double
        *stop;
    double
        *p,
        tx,
        ty,
        y;

    crossings = 0;

    tx = point-> x;
    ty = point-> y;
    y  = pgon [nbpoints - 1].y;

    p = (double *) pgon + 1;
    if ((y >= ty) != (*p >= ty))
      {
        if ((xflag0 = (pgon [nbpoints - 1].x >= tx)) ==
                (*(double *) pgon >= tx))
          {
            if (xflag0)
               crossings++;
          }
        else
            crossings += (pgon [nbpoints - 1].x - (y - ty) *
                         (*(double *) pgon - pgon [nbpoints - 1].x) /
                         (*p - y)) >= tx;
      }
     stop = &pgon [nbpoints].y;
     for (y = *p, p += 2; p <= stop; y = *p, p += 2)
       {
         if (y >= ty)
           {
             while ((p < stop) && (*p >= ty))
                 p += 2;
             if (p >= stop)
                break;
             if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
               {
                 if (xflag0)
                    crossings++;
               }
             else
                 crossings += (*(p - 3) - (*(p - 2) - ty) *
                              (*(p - 1) - *(p - 3)) /
                              (*p - *(p - 2))) >= tx;
           }
         else
           {
             while ((p < stop) && (*p < ty))
                p += 2;
             if (p >= stop)
                break;
             if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
               {
                 if (xflag0)
                    crossings++;
               }
             else
                 crossings += (*(p - 3) - (*(p - 2) - ty) *
                              (*(p - 1) -  *(p - 3)) /
                              (*p - *(p - 2))) >= tx;
           }
       }
     inside_flag = crossings & 0x01;
     return (inside_flag);
}